The term “lead” will be used herein to describe a plurality of elongate conductors covered by insulation. At a distal end of the lead, each conductor is connected to an exposed (non-insulated) electrode, or electrode contact, which is adapted to provide an electrical interface with the tissue that is to be stimulated. At a proximal end of the lead, each conductor is connected to an exposed terminal, which terminal is adapted to provide an electrical interface with a pulse generator, or with a connector of an extension lead that connects with a pulse generator. The pulse generator may be an implantable pulse generator (IPG) or an external trial stimulator (ETS), as explained hereinafter. The term “electrode array” will refer to that portion of the lead having a plurality of spaced-apart electrode contacts. The terms “electrode” and “electrode array” will be used herein interchangeably. At the proximal end of the lead, a plurality of electrical contacts, or terminals, can be connected directly to an implantable pulse generator (IPG), or as required depending upon the location where the IPG is implanted, to an electrical connector of one or more lead extensions, which lead extension(s) can be connected to the IPG. The electrode contacts on the distal end of the lead interface with tissue and can deliver a current from the IPG which causes the tissue to be stimulated. In the instance where an external trial stimulator (ETS) is required, the lead extension(s) can be connected to another type of electrical connector, referred to as an operating room (OR) connector, or trial connector, which OR or trial connector is part of or connected to an operating room (OR) cable. The OR cable can then be connected to an ETS, or similar medical equipment. The electrode contacts on the distal end of the lead interface with tissue and can deliver a current from the ETS which cause the tissue to be stimulated.
A clinical method that is well accepted in the medical field for reducing pain in certain populations of patients is known as Spinal Cord Stimulation (SCS). An SCS system typically includes an implanted pulse generator and leads, which leads are comprised of lead wires, and electrode contacts that are connected thereto. The pulse generator generates electrical pulses that are delivered to the dorsal column within the spinal cord through the electrode contacts which are implanted along the dura of the spinal cord. In a typical situation, the attached leads exit the spinal cord and are tunneled around the torso of the patient to a subcutaneous pocket where the pulse generator is implanted. Representative spinal cord stimulation systems are disclosed in the following patents: U.S. Pat. Nos. 3,646,940; 3,724,467; 3,822,708; 4,338,945; 4,379,462; 5,121,754; 5,417,719; 5,501,703; 6,516,227; and 6,895,280, which patents are incorporated herein by reference.
Electrode arrays currently used with known SCS systems may employ between one and sixteen electrode contacts on a distal end of a lead or leads. Electrode contacts are selectively programmed to act as anodes, cathodes, or disconnected (turned off), creating an electrode configuration. The number of electrode configurations available, combined with the ability of pulse-generating circuits to generate a variety of complex stimulation pulses, presents a huge selection of stimulation parameter sets to the clinician. When an SCS system is implanted, a “fitting” procedure is performed to select an effective stimulation parameter set for a particular patient. Such a session of applying various stimulation parameters and electrode configurations may be referred to as a “fitting” or “programming” session. Additionally, a series of electrode configurations to be applied to a patient may be organized in a steering programmable table or in another suitable manner.
In order to achieve an effective result from spinal cord stimulation, the lead or leads may be placed in a location such that the electrical stimulation will create a stimulation felt by the patient known as paresthesia. The paresthesia induced by the stimulation and perceived by the patient should be located in approximately the same place in the patient's body as the pain that is the target of treatment. If a lead is not correctly positioned, it is possible that the patient will receive little or no benefit from an implanted SCS system. Thus, correct lead placement can mean the difference between effective and ineffective pain therapy.
In order to test the effectiveness on a particular patient of various stimulation parameters and electrode configurations, it is often necessary to connect the lead or leads to an ETS to optimize the position of the electrode array along the dura of the spinal cord. During this intra-operative procedure, the proximal end of the lead or lead extension needs to easily connect to an intermediate operating room (OR) cable and thereafter to an ETS.
An ETS is an external device that replicates some or all of the IPG's functions and is used to evaluate the efficacy of the proposed therapy. An ETS typically includes a diagnostics module used to provide valuable feedback to the user (physician, clinician, or patient). The user can then determine whether the implanted lead is operational in delivering stimulation therapy, is reliable, and comfortable. The user then concludes if readjusting the position of the implanted lead will be necessary. The ETS is externally worn for a period of typically seven to ten days for evaluation purposes before implantation of the IPG. The ETS is typically applied with an adhesive patch to the skin of the patient, but may also be carried by the patient through the use of a belt clip or other form of convenient carrying pouch. Features of the ETS may also include: (a) usability in the operating room (OR) to test the electrode array during placement, (b) a full bi-bidirectional communication capability with the clinician's programming (CP) system, and (c) the ability to allow the patient or clinician to evaluate the stimulus levels.
In the past, the known technology has allowed only one type of single electrode lead to be connected to the OR cable at a single time. If multiple electrode arrays were to be implanted, the technology would only allow one electrode array to be tested at a single time. One obvious solution would require two OR cables and two trial stimulators. The required additional equipment for testing a multiple electrode array stimulation system would add complexity and time to the surgery. Current lead OR connectors also require alignment procedures or multiple assembly steps before the connection is complete, which also adds additional complexity and time to the “fitting” and or “programming” sessions.
As the electronic medical devices implanted in patients have become more sophisticated in providing a wider range of stimulation therapies which require multiple electrode arrays, there has arisen a critical need for a reliable, easy-to-manufacture OR connector that allows the multiple electrode array system to be detachably and reliably connected to an external trial stimulator.
It is thus evident that improvements are still needed in OR connector systems, particularly to facilitate connecting an external trial stimulator with a multiple electrode array system.